Such measuring systems are applied frequently in industrial, process measurements technology for determining values of physical and of chemical, measured variables, especially pH value, conductivity, turbidity, concentration of one or more substances, especially certain ions, such as ammonium and nitrate, or dissolved gases, as e.g. CO2 or O2, in a measured medium. Such measuring systems are especially also applied in connection with the automation of chemical or manufacturing processes and/or the automated control of industrial plants.
The sensor unit can be, for example, an electrochemical probe, especially a potentiometric or amperometric probe. Examples of potentiometric sensor types are ion selective electrodes, such as e.g. a glass electrode for measuring pH value. An example of an amperometric sensor type is a dissolved oxygen sensor working according to the principle of the Clark electrode. The sensor unit can also be a conductivity probe immersible in the medium and working according to a conductive or inductive measuring principle or an optical probe immersible in the medium, for example, for measuring turbidity according to the nephelometric or turbidimetric principle or for measuring of concentrations of certain substances, e.g. nitrate, absorbing at the wavelength of the optical probe.
For registering the respective measured variables, the sensor units have, in each case, a corresponding measuring transducer with a physical to electrical or chemical to electrical transducer, which outputs an electrical signal dependent on the value of the measured variable, as well as, connected to the measuring transducer, a circuit, as a rule, an electronic circuit, which serves for conditioning and, in given cases, further processing, the signals provided by the measuring transducer and for their forwarding to the base unit. The circuit includes for this at least one microcontroller and a data memory circuit, in which a basic software, also referred to as firmware, is stored, which provides basic functions required for processing the measuring signals. The base unit includes a data processing unit, which can process data received from the sensor unit and output the processed data via an interface to a display unit, e.g. a display, or to a superordinated unit, for example, a process control system. The base unit can be, for example, a measurement transmitter with input and display functions.
Data transmission between the sensor unit and the base unit can occur via a relay unit connected between the sensor unit and the base unit and embodied to forward, to the sensor unit, data sent from the base unit, especially measurement data, operating data, commands or software modules, and/or to forward, to the base unit, data sent from the sensor unit, especially measurement data, operating data, commands or software modules. Examples of measuring systems embodied in such a manner are described, for example, in DE 102 18 606 A1 or DE 10 2006 005633 A1. The relay unit includes in these measuring systems likewise a microcontroller, as well as at least one memory, in which is stored a basic software of the relay unit for providing the basic functionalities of the relay units. In the measuring systems described in DE 102 18 606 A1 and DE 10 2006 005633 A1, the sensor unit and the relay unit are connected releasably with one an additional via an inductively coupling, pluggable connector coupling.
In WO 2009/060001 A1, a measuring point for determining a value of a physical or chemical, measured variable of a medium is described, wherein the measuring point includes a base unit and a sensor unit, wherein the sensor unit is connectable releasably with the base unit via a pluggable connector coupling. The base unit is provided for energy supply of the sensor unit, for data exchange with the sensor unit and for communication to a process monitoring facility of a signal representing the value of the measured variable. It includes a first microprocessor for conditioning data received from the sensor unit, for communication to the process monitoring facility and a data memory for the storage of measuring point specific data. The sensor unit includes a primary sensor with a transducer, which outputs an electrical signal dependent on the value of the measured variable, and a circuit for conditioning the transducer signals, wherein the circuit includes an A/D converter and a second microprocessor for processing digitized signals and a data memory, in which sensor specific data are stored, as well as a program memory, which contains a low level software with basic functionalities for the operation of the sensor unit. Via an inductive interface, via which the energy supply of the sensor unit by the base unit and the data exchange with the base unit occurs, at least one software module is transmittable from the base unit to the sensor unit and storable in the program memory of the sensor unit, wherein the software module contains supplemental functions for monitoring the primary sensor. In this way, low level software stored in the program memory of the sensor unit can be updated.
In the case of the measuring systems known from the state of the art, it is, however, not provided, also to update a basic software, especially a low level, basic software, of the relay unit providing the basic functions of the relay unit.